In general, a silver halide black-and-white photographic material is processed through processing steps such as black-and-white development, fixing and water washing after exposure, and a silver halide color photographic material (hereinafter referred to as color photographic material) is processed through processing steps such as color development, desilvering, water washing and stabilization after exposure. A silver halide color reversal photographic material is processed through processing steps such as black-and-white development after exposure and color development, desilverization, water washing and stabilization after reversal processing.
In the case of color development, exposed silver halide grains are reduced to silver by a color developing agent and the oxidation product of the color developing agent reacts with a coupler to form an image dye during the color development step.
In the subsequent desilverization step, the developed silver generated during development is oxidized (bleached) to silver salt by the bleaching agent (oxidizing agent) and then removed (fixed) from the light-sensitive layer together with unexposed silver halide by the fixing agent capable of forming a soluble silver. The bleaching and fixing may be conducted separately as the bleaching step and the fixing step or may be conducted simultaneously as the bleach-fixing step. The details on these processing steps as well as on the processing compositions therefor are described in James, The Theory of Photographic Process, 4th ed. (1977), Research Disclosure No. 17643, Items 28 and 29, ibid., No. 18716, from left column to right column at 651, ibid., No. 307105, Items 880 and 881.
In addition to the above-described fundamental processing steps, various auxiliary steps may be provided so as to maintain photographic and physical qualities of the dye image or to ensure the safety in processing. Examples thereof include water washing step, stabilization step, film hardening step and stopping step.
Further, the developed silver halide black-and-white photographic material is processed with a reducer containing an oxidizing agent so as to control the gradation and the like.
The oxidizing agent added to the processing solution for use in the above-described bleaching or reducing is generally ethylenediaminetetraacetato ferric complex salt or 1,3-diaminopropanetetraacetato ferric complex salt, which is hardly biodegraded. Recently, from the standpoint of environmental conservation, the photographic processing solution exhausted from these photographic processings has been demanded to cause no nuisance and accordingly, an alternative to the above-described bleaching agent insusceptible of biodegradation has been investigated.
The bleaching agent having biodegradability includes a ferric complex salt of N-(2-carboxymethoxyphenyl)iminodiacetic acid disclosed in West German Patent (OLS) No. 3,912,551, ferric complex salts of .beta.-alaninediacetic acid and of glycine dipropionic acid disclosed in EP-A-430000, and a ferric complex salt of ethylenediamine-N,N'-disuccinic acid disclosed in JP-A-5-72695 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, the processing solution having bleaching ability and comprising such a bleaching agent cannot be said satisfactory in its desilvering property and it has been found that, when a continuous processing is conducted using such a solution, there arise problems that the desilvering property is reduced as compared with the initial stage of the continuous processing, that the bleaching fog increases and that the prevention of stains due to aging is insufficient.
It has recently become popular to conduct the color development in a miniaturized automatic developer called mini-lab so as to provide rapid processing service to users, in which the stability in performance is indispensable for a continuous processing, to say nothing of rapid bleaching.
Further, the metal chelating compound used as a bleaching agent has been demanded to have a reduced concentration in view also of environmental conservation. However, the above-described bleaching agents in a dilute concentration have failed to provide sufficient desilverization.